1. Field of Invention
The present invention relates to communications systems and, more particularly, to a physical layer structure of a waveform for use in wireless communications systems.
2. Discussion of Related Art
Most existing communication waveforms used in conventional wireless telecommunication systems generally rely on network topologies that have a fixed infrastructure, such as, for example, a “hub and spoke” network topology used by most cellular communications networks. The hub and spoke network topology typically comprises a fixed central node that is configured to coordinate the operation of other nodes in the network. One example of a hub-spoke network topology is a WI-FI system based on the IEEE 802.11 standard.
Some communication systems however use informal infrastructures rather than fixed infrastructures. For example, a telecommunication system having no formal structure is a Mobile-Ad-hoc Network (MANET). A MANET is a self-configuring network of mobile nodes connected by wireless links. Each node in a MANET is generally free to move independently in any direction and therefore its ability to communicate with other nodes may change frequently. The nodes in a MANET may be transported by people, vehicles, projectiles or any of numerous other mobile platforms. Existing waveforms that rely on fixed infrastructure are not designed to support high relative velocity between network nodes, which can frequently occur in a MANET environment. In addition, because the nodes of a MANET are generally moving in an arbitrary manner, the wireless link conditions may change frequently due to changing environmental conditions as the nodes move, and existing waveforms are ill-equipped to deal with such rapidly changing link conditions.